In modern hybrid and electric motor vehicles, lithium-ion batteries are often used as rechargeable energy stores. A battery system which is optimized with regard to lifespan and maximum energy storage amount requires for the individual cells of a complete battery system—which are to be designated below as “battery units”—a correspondingly efficiently dimensioned cooling system, which is able to prevent an overheating of the battery units beyond a maximum permissible operating temperature. From the prior art, in this connection, is the integration of such a cooling system, which—based on the vaporizer principle known to the specialist in the art—permits a heat exchange via structurally suitably constructed cooling plates between the battery units and a liquid coolant flowing through the cooling ducts, wherein the enthalpy of vaporization necessary for the vaporizing of the liquid coolant is taken from the battery units in the form of heat. In order to now keep the manufacturing costs as low as possible for such a cooling device, it is usual to construct this with several individual cooling plates, wherein a particular battery unit of the entire battery system is associated with each cooling plate. Such a modular approach allows the size and therefore the efficiency both of the battery system and also of the cooling device necessary for the cooling of the battery system to be adapted to the most varied of requirements. Thus, a battery system of modular construction with two battery units and consequently cooling plates necessary for the cooling thereof may be sufficient for installation in a small car, whereas a battery system of such dimensions must be supplemented by two further battery units including two additional cooling plates for use in a limousine.
However, it proves to be problematic in such cooling devices of modular construction to achieve a uniform, i.e. homogeneous cooling efficiency in the individual cooling plates both relative to one another and also within a single cooling plate. As the vaporization temperature of the coolant is dependent on the fluid pressure in the fluid ducts and this decreases as a consequence of the drop in pressure occurring continuously during the flowing through of the individual cooling plates, the temperature also changes at which the initially liquid coolant vaporizes. This leads, in turn, to undesired inhomogeneities in the temperature distribution of the coolant within the cooling plate. This effect proves to be problematic to a particular extent when the entire cooling device is operated as part of a regulating circuit which adjusts the actual temperature actually measured in the battery units to a predetermined desired value.